VS pin voltage going higher than supply

Question

In LTSpice I'm modeling a simple circuit using the AD8210. For space applications we are placing a 4.99&Omega; resistor in series with the VS pin. I noticed in the sim, that the VS pin will go up to 6V when supplied with 5V. 
 With the normally low current draw, the resistor doesn't cause a drop issue. But in this circuit I'm getting a boost beyond the circuit specs when I add this resistor. I would have expected ~10mV drop, not a 1V boost! 
 Is this just a spice model issue? Can anyone confirm with the real chip? 
 Thanks! 
 Aaron

Alager · Accepted Answer

Gilbeys, 
 Thanks for trying it out. I noticed that your example schematic doesn't have a ground connection to the chip. So I played around with the connections on my circuit. It looks like as soon as I connect the VIN- pin to ground, then I get the weird behavior. 
 I also noticed that I had forgotten to put the shunt resistor in, once I put a 100m&Omega; resistor across VIN+ and VIN- the weirdness went away. 
 So, with VIN- grounded and no shunt = weird. Add the shunt and all is normal.)

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VS pin voltage going higher than supply